The haptor is the attachment organ of the monogeneans, a group of parasitic Platyhelminthes. The haptor is sometimes called opisthaptor (from opistho-: behind) to emphasize that it is located in the posterior part of the body, and to differentiate it from the prohaptor (from pro-: in front), a structure including glands located at the anterior part of the body. According to Yamaguti (1963),the chief adhesive organ of the monogeneans, the haptor, is posterior, more or less discoid, muscular, may be divided into alveoli or loculi, is usually provided with anchors, has nearly always marginal larval hooklets, or is in a reduced form with anchors. The haptor may consist of symmetrical or asymmetrical, sessile or pedunculate, muscular suckers or clamps with or without supporting sclerites; accessory adhesive organs may be present in form of armed plaques, lappets or appendices.
Monogeneans are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish. They have a direct lifecycle and do not require an intermediate host. Adults are hermaphrodites, meaning they have both male and female reproductive structures. Monogeneans have a series of hooks which are used to attach onto fish, and as a result, could lead to infections.
Satyu Yamaguti was a Japanese parasitologist, entomologist, and helminthologist. He was a specialist of mosquitoes, and helminths such as digeneans, monogeneans, cestodes, acanthocephalans and nematodes. He also worked on the parasitic crustaceans Copepoda and Branchiura. Satyu Yamaguti wrote more than 60 scientific papers and, more importantly, several huge monographs which are still in use by scientists all over the world and were cited over 1,000 times each.
A sucker in zoology refers to specialised attachment organ of an animal. It acts as an adhesion device in parasitic worms, several flatworms, cephalopods, certain fishes, amphibians, and bats. It is a muscular structure for suction on a host or substrate. In parasitic annelids, flatworms and roundworms, suckers are the organs of attachment to the host tissues. In tapeworms and flukes, they are a parasitic adaptation for attachment on the internal tissues of the host, such as intestines and blood vessels. In roundworms and flatworms they serve as attachment between individuals particularly during mating. In annelids, a sucker can be both a functional mouth and a locomotory organ. The structure and number of suckers are often used as basic taxonomic diagnosis between different species, since they are unique in each species. In tapeworms there are two distinct classes of suckers, namely "bothridia" for true suckers, and "bothria" for false suckers. In digeneal flukes there are usually an oral sucker at the mouth and a ventral sucker posterior to the mouth. Roundworms have their sucker just in front of the anus; hence it is often called a pre-anal sucker.
The structure of the haptor is different in the two major groups constituting the Monogenea, namely the Polyopisthocotylea and the Monopisthocotylea, and is an important part of the diagnosis in both groups.
Polyopisthocotylea is a subclass of parasitic flatworms in the class Monogenea.
The Monopisthocotylea are a subclass of parasitic flatworms in the class Monogenea.
The Diplectanidae are a family of monopisthocotylean monogeneans. They are all parasitic on the gills of fish. Diplectanids are small animals, generally around 1 mm in length. As parasites, they can be extremely numerous, up to several thousand on an individual fish.
Squamodiscs are epidermal structures, which are typical of and found only in certain monogeneans of the family Diplectanidae. There are, typically, two squamodiscs, one ventral and one dorsal, located on the haptor of the monogenean. Squamodiscs are usually made up of scales embedded in the epidermis, which appear from the outside as rodlets arranged in rows.
Lamellodiscs are epidermal structures, which are typical of and found only in certain monogeneans of the family Diplectanidae. There are, typically, two lamellodiscs, one ventral and one dorsal, located on the haptor of the monogenean. Lamellodiscs are made up of concentric lamellae embedded in the epidermis. Lamellodiscs are considered as special type of squamodiscs, which are homologous structure found in many diplectanid monogeneans but formed of rows of rodlets instead of lamellae
Protomicrocotylidae is a family of monogenean parasites in the order Mazocraeidea.
Clamps are the main attachment structure of the Polyopisthocotylean monogeneans.
These ectoparasitic worms have a variable number of clamps on their haptor ; each clamp is attached to the host fish, generally to its gill. Clamps include sclerotised elements, called the sclerites, and muscles. The structure of clamps varies according to the groups within the Polyopisthocotylean monogeneans; microcotylids have relatively simple clamps, whereas gastrocotylids have more complex clamps.
Lethacotyle is a genus of polyopisthocotylean monogeneans, included in the family Protomicrocotylidae.
The genus includes only two species: Lethacotyle fijiensisManter & Price, 1953 , the type-species of the genus, and Lethacotyle veraJustine, Rahmouni, Gey, Schoelinck, & Hoberg, 2013 . Both species are parasitic on the gills of jacks in the Pacific Ocean. They are known only from three localities: off Fiji, Andaman Islands, and New Caledonia.
The genus Lethacotyle is special in that its members have no clamps on their posterior attachment organ or haptor, in contrast to most polyopisthocotylean Monogenean which have clamps. This is reflected in the etymology of the name, which, according to Manter & Price is "from letha = forgetting, and cotyle = cup, and refers to the absence of clamps".
Lethacotyle vera is a species of monogenean of the family Protomicrocotylidae.
Chimaericola leptogaster is a species of polyopisthocotylean monogenean in the family Chimaericolidae. It is ectoparasitic on the gills of the chimaera Chimaera monstrosa.
Pseudorhabdosynochus bocquetae is a diplectanid monogenean parasitic on the gills of groupers. It has been described in 1984 by Guy Oliver and Ilan Paperna. The species was first described as Cycloplectanum bocquetae and transferred to the genus Pseudorhabdosynochus by Delane C. Kritsky and Mary Beverley-Burton in 1986.
Microcotyle bothi is a species of monogenean, parasitic on the gills of a marine fish collected in Hawaii. It belongs to the family Microcotylidae.
Microcotyle fusiformis is a species of monogenean, parasitic on the gills of a marine fish, described by Seitarō Gotōin 1894. It belongs to the family Microcotylidae. This species was first.
Microcotyle polymixiae is a species of monogenean, parasitic on the gills of a marine fish. It belongs to the family Microcotylidae. It was first described and illustrated based on 82 whole mounts, from the gills of the silver eye, Polymixia japonica (Polymixiidae) off Hawaii..
Pseudorhabdosynochus hargisi is species of a diplectanid monogenean parasitic on the gills of the White grouper Epinephelus aeneus. It was described in 1984 as Diplectanum hargisi and transferred to the genus Pseudorhabdosynochus by Santos, Buchmann & Gibson in 2000. Its systematic position has been clarified by Kritsky, Bakenhaster & Adams in 2015, who differentiated it from Pseudorhabdosynochus americanus.
Pseudorhabdosynochus riouxi is a species of diplectanid monogenean parasitic on the gills of dusky grouper Mycteroperca marginata. It was described by Guy Oliver in 1986 as Cycloplectanum riouxi, then transferred to the genus Pseudorhabdosynochus by Santos, Buchmann & Gibson in 2000. The species has been redescribed by Chaabane et al. in 2017.
Microcotyle gimpo is a species of monogenean, parasitic on the gills of a marine fish. It belongs to the family Microcotylidae.
Microcotyle sebastis is a species of monogenean, parasitic on the gills of a marine fish. It belongs to the family Microcotylidae.
Pseudaxine is a genus which belongs to the phylum Platyhelminthes and class Monogenea; all its species are parasites of fish.
Pseudaxine trachuri is a species of monogenean, parasitic on the gills of a marine fish. It belongs to the family Gastrocotylidae.
Pseudaxine indicana is a species of monogenean flatworm, which is parasitic on the gills of a marine fish. It belongs to the family Gastrocotylidae.
Sibitrema is a genus which belongs to the phylum Platyhelminthes and class Monogenea; the only species included in this genus is parasite of fish.